Labyrinth seal repair
A method and apparatus for repairing damaged fins in a labyrinth seal, the seal without the use of welding or metallurgical bonding. The method comprises the steps of removing a section of the shaft containing the damaged fins, and providing a sleeve with replacement fins.
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The invention relates to repair of a labyrinth seal and a replacement component for use therein.
BACKGROUND OF THE ARTThe invention relates to repair of a labyrinth seal, particularly in a fan rotor in gas turbine engines wherein the seal is formed on a shaft that rotates in relation to another moving or stationary runner surface.
The air seal comprises the fan rotor with labyrinth seal fins, which rotates, and a concentric shaft known as the seal runner which is stationary. Frequently, a bearing contained in a bearing compartment supports the motion of the two shafts. The bearing compartment contains oil lubricant which must be contained within the compartment. The oil must be confined to the bearing chamber by using a seal. In this instance the oil is retained in the bearing chamber by using an air pressurized labyrinth seal.
A labyrinth seal is useful in sealing an air-oil interface in gas turbine engines. If the seal fins are damaged or incorrectly manufactured, however, the sealing of the bearing compartment may be jeopardized and result in oil leakage. If the oil leakage is excessive, the fan rotor will have to be replaced and scrapped. This is expensive and wasteful. Alternatively, the seal may be repaired by removing and replacing only the damaged fins. Challenges in repairing the damaged fins include the limited line of sight access of the fins within the fan rotor, the structural integrity of the fan rotor and the precision of the labyrinth seal dimensions.
Existing repair methods use weld repair build-up and subsequent re-machining of the fins to the required dimensions, however this approach presents several drawbacks. Accordingly, there is room for improvement.
SUMMARY OF THE INVENTIONOne aspect of the present invention is a method for replacing at least one damaged fin in a labyrinth seal comprising the steps of: removing a section of the labyrinth seal containing the damaged fin, thus forming a recess; providing a sleeve with at least one replacement fin; and fitting the sleeve into the recess, the sleeve being attached to the labyrinth seal by way of an interference fit with the labyrinth seal.
Another aspect of the present invention is a sleeve for replacing at least one damaged fin of a labyrinth seal, the damaged fin being on a section removed from the labyrinth seal, thus forming a recess, the sleeve comprising at least one replacement fin, wherein the sleeve fits into the recess and is attached by way of an interference fit.
Another aspect of the present invention is a turbine engine having a labyrinth seal, the labyrinth seal having a plurality of fins, wherein the labyrinth seal comprises a sleeve attached by way of an interference fit, and at least one of the plurality of fins is formed on the sleeve.
Features that distinguish the present invention from the background art will be apparent from review of the disclosure, drawings and description of the invention presented herein.
In order that the invention may be readily understood, one embodiment of the invention is illustrated by way of example in the accompanying drawings.
Further details of the invention and its advantages will be apparent from the detailed description included below.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTSA fan rotor in the gas turbine engine comprises an inner shaft 12 and a concentric outer stationary shell 13. Bearings 14 in an enclosed bearing compartment 15 supports the rotation of the inner shaft 12 relative to the shell 13. Integral with the inner shaft 12 is a labyrinth seal 16, with a plurality of fins 17 in close proximity to a seal runner 18 on the bearing compartment. When the fan rotor is in operation, air pressure from the inside of the shaft 12 flows through radial holes in the shaft and flows through the radial gap in the air seal thus preventing the oil from escaping.
In
Shown in
The sleeve 21 is then fitted into the inner shaft 12 by interference fitting techniques known in the art. One preferred method of interference fitting is to heat up the sleeve 21 to achieve an expansion of the sleeve diameter, and to cool down the inner shaft 12 to achieve a shrinkage of the shaft diameter. The expanded sleeve 21 is fitted over the shrunken inner shaft 12 and both are allowed to return to room temperature. This causes the sleeve 21 and the inner shaft 12 to engage each other in a tight fit. Other interference fitting techniques are possible, such as press fitting with a hydraulic ram or clamping. As shown in
The use of an interference fit instead of an interlocking fit between the inner shaft 12 and the sleeve 21 allows for simpler machining operations. This is not only quicker and less expensive, but also reduces possible wear to the parts. Additionally, the removed section can be shallow so that the strength of the inner shaft 12 is not significantly reduced.
Although the above description relates to a specific preferred embodiment as presently contemplated by the inventor, it will be understood that the invention in its broad aspect includes mechanical and functional equivalents of the elements described herein.
Claims
1. A method for replacing at least one damaged fin in a labyrinth seal comprising the steps of:
- removing a section of the labyrinth seal containing the damaged fin, thus forming a recess;
- providing a sleeve with at least one replacement fin; and
- fitting the sleeve into the recess, the sleeve being attached to the labyrinth seal by way of an interference fit with the labyrinth seal.
2. The method of claim 1 wherein the step of removing the section comprises machining.
3. The method of claim 1 wherein the step of fitting the sleeve does not involve application of heat and does not involve metallurgical bonding.
4. The method of claim 1 wherein the step of removing the section comprises removing a plurality of fins, and the sleeve comprises a plurality of replacement fins equal in number to the removed fins.
5. The method of claim 1 wherein the labyrinth seal is on a shaft, and the step of fitting the sleeve comprises heating the sleeve and cooling the shaft.
6. The method of claim 1 wherein the labyrinth seal is in a gas turbine engine.
7. A sleeve for replacing at least one damaged fin of a labyrinth seal, the damaged fin being on a section removed from the labyrinth seal, thus forming a recess, the sleeve comprising at least one replacement fin, wherein the sleeve fits into the recess and is attached by way of an interference fit.
8. A turbine engine having a labyrinth seal, the labyrinth seal having a plurality of fins, wherein the labyrinth seal comprises a sleeve attached by way of an interference fit, and at least one of the plurality of fins is formed on the sleeve.
Type: Application
Filed: Sep 28, 2006
Publication Date: Apr 3, 2008
Patent Grant number: 7726021
Applicant:
Inventor: Barry Barnett (Markham)
Application Number: 11/528,648